Active Stress during Compression Testing of Various Foods Measured Using a Multiple-point Sheet Sensor

Using a multiple-point sheet sensor (MSS), load and contact area were directly measured for compression of four different foods. The MSS provided temporal and spatial changes in stress applied on the sample surface during the testing. The sum of load value detected by the MSS corresponded to the load measured by a universal testing machine during the compression. The contact area between a flat probe and food surface varied with the variety of foods even though under a small strain, and increased as compression strain increased. The active stress, that is, the load divided by the contact area, was different from conventional stress, that is, the load divided by the initial cross-sectional area. The value of active stress provided a better explanation of textural characteristics of food, because texture is often sensed under a large deformation and mixed assessment of mechanical and geometrical properties.